Se o gato começar a miar de madrugada, eu não chego a voltar a adormecer.

Because after se referring to a future possibility, Portuguese uses the future subjunctive.

So:

• Se o gato começar... = if the cat starts...
• not Se o gato começa... in this meaning

A useful thing to know is that for many regular verbs, the future subjunctive form looks exactly like the infinitive. So começar here is not just an infinitive by chance; it is also the correct future subjunctive form.

You can see this more clearly with an irregular verb:

• Se ele for... = if he goes...
• not Se ele vai...

So in this sentence, começar is the normal and correct form.

Because começar a + infinitive means to begin/start to do something.

So:

• começar a miar = to start meowing
• começar a falar = to start speaking
• começar a chover = to start raining

In European Portuguese, this structure is very standard and natural.

De madrugada means in the early hours of the morning, usually while it is still dark. In everyday English, depending on context, it often comes out as:

• in the middle of the night
• in the early hours
• at some ungodly hour
• sometimes before dawn

It does not usually mean the same as broad daylight morning. It refers to that late-night / pre-dawn period.

Miar is the infinitive of the verb to meow.

After começar a, Portuguese uses the infinitive:

• começar a miar = to start meowing

So miar is not a special form here; it is simply the base verb form used after the preposition a.

This is a very common point of confusion.
Chegar a + infinitive can mean something like:

• to get to the point of
• to manage to
• to even
• to end up

In a negative sentence, não chegar a + infinitive often means not even to manage to or not to get as far as doing something.

So:

• não chego a voltar a adormecer

means more than just I don’t fall asleep again. It suggests:

• I don’t even manage to get back to sleep
• I never get back to sleep
• I don’t manage to fall asleep again

It adds emphasis.

Because there are two separate verb patterns:

1. chegar a + infinitive

   • chego a voltar...

2. voltar a + infinitive

   • voltar a adormecer

So the full chain is:

• chego a
  • voltar a
    • adormecer

Each a belongs to a different verb construction. This is completely normal.

This is an important vocabulary distinction.

• dormir = to sleep, to be asleep
• adormecer = to fall asleep

So:

• voltar a dormir can suggest to go back to sleeping
• voltar a adormecer specifically means to fall asleep again

In this sentence, the speaker wakes up because of the cat and then cannot fall asleep again, so adormecer is the right choice.

Because the idea is to fall asleep again, not simply to fall asleep.

The speaker was already asleep, then woke up because the cat started meowing, and after that could not get back to sleep.

So:

• adormecer = fall asleep
• voltar a adormecer = fall asleep again / get back to sleep

The word voltar adds the idea of returning to a previous state.

Because the sentence expresses a general result or a habitual reaction.

It is basically saying:

• If the cat starts meowing in the early hours, I don’t manage to get back to sleep.

That is a general truth for the speaker, so the present tense is natural.

Portuguese often uses:

• se + future subjunctive in the condition
• present tense in the result

when talking about something that generally happens.

If you wanted to talk about one specific future situation, a future form in the second clause could also be possible, but the present here sounds very natural and idiomatic.

No. Portuguese often drops subject pronouns when the verb already makes the subject clear.

So both are possible:

• eu não chego a voltar a adormecer
• não chego a voltar a adormecer

Including eu can add a little emphasis, contrast, or personal focus. It is not wrong at all; it just is not strictly necessary.

Because the sentence begins with a conditional se clause:

• Se o gato começar a miar de madrugada, ...

When that clause comes first, it is normally separated from the main clause with a comma.

So the structure is:

• If X happens, Y happens.

This is the same basic punctuation logic as in English.

Yes. Não chego a voltar a adormecer is a bit more expressive.

Compare:

• não volto a adormecer = I don’t fall asleep again
• não chego a voltar a adormecer = I don’t even manage to get back to sleep

The version with chego a highlights the failure to reach that point. It sounds a little more vivid and idiomatic.

Yes, absolutely.

• não consigo voltar a adormecer = I can’t get back to sleep

This is very natural and perhaps more straightforward for a learner.

Compared with that:

• não chego a voltar a adormecer

has a slightly different nuance. It suggests I never even get as far as falling asleep again. It is a bit more idiomatic and emphatic.

Yes, it sounds natural in European Portuguese.

Several features fit very well with normal European Portuguese usage:

• Se + future subjunctive
• começar a + infinitive
• de madrugada
• voltar a adormecer
• chegar a + infinitive for emphasis

A learner should understand this as a normal, idiomatic sentence, not as something unusually literary or strange.